You raise a good question. The concept of "free and unlimited" energy is not new, in fact it is arguable that this idea is what got us into the trouble we're in to begin with (http://en.wikipedia.org/wiki/Too_cheap_to_meter).…"
"Useful information is the Coefficient of Performance (COP) of the whole house fan vs. alternatives. The true answer is more complicated than that, since all equipment has a COP "curve" that flattens out as the delta-T between inside and…"
"Thanks for the input. The next question to ask is "how much cooling power is delivered in each case?" Whole house fans work best when the house is hot and the air is cold. Either of those things change and they work less well. I am not…"
The "large fan" is a whole house fan moving anything from 1000-4000 CFM. By comparison, the ventilation system for the T24 prototype home we modeled was 67 CFM. As you might imagine, a fan that moves 1000-4000 CFM could use a lot of…"
"I think it is important to check the energy consumption of such a large fan, even assuming it can be properly air-sealed and insulated. We are finishing up a study on 2013 Code vs. Passive House in each of California's climate zones and, while…"
"Good point, but the Passive House system is also running continuously, which would tend toward higher capture efficiency as contrasted to a situation with low vented range hood usage. While the intermittent rate may be higher, its duty cycle may be…"
"If you applied 100 CFM to the kitchen on demand, it would meet the 62.2 requirement, but you would be over-ventilating, since there is a continuous exhaust function occurring 24/7 in addition. Passive House aims for ~0.3 ACH continuous ventilation…"
"This is pretty unsettling! To clarify, the presence of a recirculating hood is not a code violation, the absence of an exhausting hood is the code violation, in residential buildings with three or fewer stories. In Passive House, both a…"
"0.006 ACH50 would be better, but not feasibly attainable. 1.5 vs 0.6 ACH50 makes a big difference when you're aiming for Passive House levels of performance. I am not experienced enough to expound on the cost curve of air tightness, but I know…"
"True, a vessel leaking water at the same rate would lose more energy, but since the "vessel" in question is a building, it is filled with conditioned air, not water, and leaks are insidious.
Solar gains help to a point, but tend to be…"
"I take issue with your reasoning. Since Passive House is a performance metric, the climate is irrelevant in terms of marginal return analysis. Except for the air tightness, which is set at the same level in all climates, everything else is climate…"
"It's interesting to me that ASHRAE 62.2 requires a kitchen exhaust vented directly to the interior at either 100 CFM intermittent or 5 ACH continuous, both of which are higher than the typical "hybrid" Passive House approach where a…"
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